This application is based on Japanese Patent Application No. 11-163005 (1999) filed Jun. 9, 1999, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a method for manufacturing an ink jet recording head, an ink jet recording head, and an ink jet recording apparatus, and in particular, to a method for manufacturing an ink jet recording head by means of wet etching using an etchant.
2. Description of the Related Art
To manufacture a so-called xe2x80x9cside-shooter typexe2x80x9d ink jet recording head that injects inks in a substantially perpendicular direction onto a substrate having injection energy generating elements, ink supply ports are produced by forming through-holes in the substrate having the ink injection energy generating elements. In this type of recording head, the inks are supplied from a rear side of the substrate via the ink supply ports.
Methods for manufacturing such an ink jet recording head are known, for example, from Japanese Patent Application Laid-open No. 62-264957 (1987) and U.S. Pat. No. 4,789,425. These methods use mechanical processing such as sand blasting or ultrasonic grinding to form the above described through-holes in the substrate with the injection energy generating elements formed thereon and then form grooves constituting ink channels. The ink channels or the like may be formed before the throughholes. Then, an electroforming plate with ink injection openings formed therein is bonded to the substrate while aligning the ink injection openings with the ink channels or the like in the substrate.
To achieve a reduced size, an increased density, or the like, recently known ink jet recording heads have an electric drive circuit (a diode matrix circuit or a shift register circuit) formed on the substrate for driving the injection energy generating elements. When such highly-functional recording heads are manufactured and if the above described mechanical processing such as sand blasting or ultrasonic grinding is used to form the ink supply ports, relatively much attention must be paid to handling of the processing. This is because the above described drive circuit is very sensitive to static electricity and vibration, so that the above processing method may affect the characteristics of the circuit.
Thus, as means for solving this problem, a method has been proposed which uses silicon as a substrate material and which uses wet etching to form the through-holes for the ink supply ports from the rear surface of the substrate. Since this method forms the through-holes by means of chemical etching, which step of the ink jet recording head manufacturing process is used for this formation can be set substantially arbitrarily. That is, the through-holes can also be formed during the final step where principal functional parts of the ink jet recording head have already been formed. Compared to the formation of the ink supply ports based on the mechanical processing which is executed relatively early during the recording head manufacturing process, the method allowing the through-holes to be formed during the final step can advantageously solve problems such as a decrease in the strength of the substrate caused by the through-holes formed during an initial step, the decrease in turn making handling of the substrate complicated during the subsequent manufacturing steps.
In the wet etching for silicon, anisotropic etching using an alkaline etchant is commonly performed, which has the advantage of increasing the density of a formed circuit pattern or the like. An etching mask for an etching start surface is composed of an inorganic film, for example, a silicon oxide film or a silicon nitride film. The etchant is prepared from TMAH (tetramethylammonium hydroxide), KOH, hydrazine, or the like which provides different etching speeds depending on crystal faces.
With such wet etching, the substrate with the injection energy generating elements and a circuit of drive elements therefor formed thereon has its top surface (hereinafter, referred to as xe2x80x9cdevice surfacexe2x80x9d) exposed to the etchant, a configuration for protecting these circuits is required. Conventionally known such configurations include a method of using a jig to cover the circuit on the substrate in order to protect them from the etchant, a method of bringing the etching start surface (rear surface) of the silicon substrate into contact with a bath with the etchant overflowing therefrom, without immersing the substrate in the etchant, and a method of applying an etching-protective film to a device surface of the substrate before etching.
However, these configurations for protecting the device surface of the substrate from the etchant have the following problems:
With the method of using the jig for the device surface of the substrate or bringing the etching start surface of the substrate into contact with the overflowing surface of the etchant, inappropriate setting of the jig on the substrate or inappropriate control of the overflowing etchant surface may cause the etchant to flow onto the top surface of the substrate to damage functional elements such as the injection energy generating elements and drive elements as well as their circuit. The damage to the circuit means corrosion of exposed wiring of the circuit and/or an electrode section with the etchant or destruction of the injection energy generating elements and drive elements therefor.
Further, the above methods of using the jig and bringing the substrate into contact with the overflowing substrate are disadvantageous in productivity, particularly, in efficiency. That is, massive batch processing, which is an advantage of wet etching, is difficult with these methods.
In general, TMAH is used as the etchant taking safety and adverse effects on environments into consideration. In this case, the etching requires 10 to 30 hours if the silicon substrate has a thickness of, for example, 625 xcexcm. Consequently, this method requires a very long time for a massive batch process and is thus substantially incompatible with such a process, resulting in a reduced production efficiency.
The another above-described method for protecting the functional elements and circuit on the substrate, that is, the method of coating an etching-protective layer on the device surface of the substrate forms the protective film by coating the device surface with a molten wax or the like or coating and drying a negative-type photoresist thereon. Although, however, such a protective film is not modified by alkaline etchants, it does not adhere to a ground layer (as a protective layer for the circuit, an inorganic film, for example, a silicon dioxide film, a silicon nitride film, or the like is typically formed between the substrate and the protective layer) and may be released from the substrate (particularly from its peripheries). As a result, the circuit and elements on the substrate, especially exposed wirings and electrodes of the circuit, tantalum(Ta) used in a protection for heater materials, and defects or inefficiently covered portions of the ground layer, may come in contact with the etchant and may be damaged.
It is an object of the present invention to solve the above described problems of the prior art in order to provide a method for manufacturing an ink head recording head using wet etching, the method being able to carry out etching while maintaining a high production efficiency, an ink jet recording head manufactured using this method, and an ink jet recording apparatus using this ink jet recording head.
To attain the above object, a method for manufacturing an ink jet recording head according to the present invention is characterized by comprising the steps of providing a substrate having a device surface with elements constituting an ink jet recording head, forming an adhesive layer in peripheries of the device surface, forming, in contact with the adhesive layer, an etching-protective layer for protecting the device surface from an etchant, etching the substrate by the etchant, and removing the etching-protective layer.
In addition, an ink jet recording head according to the present invention is characterized by being manufactured by means of a manufacturing method comprising the steps of providing a substrate having a device surface with elements constituting an ink jet recording head, forming an adhesive layer in peripheries of the device surface, forming, in contact with the adhesive layer, an etching-protective layer for protecting the device surface from an etchant, etching the substrate by the etchant, and removing the etching-protective layer.
Further, an ink jet recording apparatus is characterized by carrying out recording using an ink jet recording head for injecting inks, the ink jet recording head being manufactured by means of a manufacturing method comprising the steps of providing a substrate having a device surface with elements constituting an ink jet recording head, forming an adhesive layer in peripheries of the device surface, forming, in contact with the adhesive layer, an etching-protective layer for protecting the device surface from an etchant, etching the substrate by the etchant, and removing the etching-protective layer.
In the above configuration, when the protective layer for the etchant is used, the adhesive layer is formed on areas where the protective layer and the substrate are in contact. Consequently, the adhesion between the protective film and the substrate can be improved to prevent the functional elements and circuit in the ink jet recording head from being damaged by the etchant. As a result, when ink supply ports are formed by means of wet etching, the device surface is protected from damage, thereby enabling manufacturing of an ink jet recording head with a high yield and an improved production efficiency.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.